docs: def str_repr(klass):
      """
      Implements string conversion methods for the given class.
  
      The given class must implement the __str__ method. This decorat
      will add __repr__ and __unicode__ (for Python 2).
  
      """
      if PY2:
          klass.__unicode__ = klass.__str__
          klass.__str__ = lambda self: self.__unicode__().encode('utf-8')
      klass.__repr__ = lambda self: '<%s: %r>' % (self.__class__.__name__, str(self))
      return klass